I got Rambo blue buffalo freedom LBP because that's what the breeder was feeding him. His stool is solid in the morning but as the day goes on it gets looser and by the time he goes at night it's pudding-like. So I decided to switch him over and I bought Fromm LBP. I know i need to change his food slowly. How slow? I usually give him 1/2 cup of blue buffalo. How much Fromm should I put in there? Will it take a few days? Weeks?